L.A. air pollution may increase risk of stroke

A stretch of the California State Route 99 corridor in the San Joaquin Valley… (Gary Kazanjian / Associated…)

L.A.’s smog problem might not be as visible as it was in the bad old days of the 1970s and '80s, but city residents might be at an increased risk of stroke even at levels of pollution that meet EPA standards. Oh yeah, and memory loss.

A new study published Monday in the Archives of Internal Medicine found that Boston residents experienced more strokes when exposed to “moderate” amounts of particulate air pollution, as opposed to “good” amounts of pollution, according to EPA standards. The types of pollution monitored included those specifically linked with car traffic.

Reviewing the medical records of about 1,700 stroke victims at Boston’s Beth Israel Deaconess Medical Center, the study’s authors found that the risk of stroke was 34% higher on days of “moderate” exposure than it was on “good” days. The effects were most acute in the first 12 to 14 hours after exposure.

“The main message is that, at levels that are below the current EPA standards that are considered safe, we were seeing a rather large increase in risk of stroke in association with particulate air pollution,” said George Wellenius, an assistant professor of Epidemiology at Brown University and lead author of the study.

Particulate air pollution, or ambient particles, includes fine particles less than 2.5 micrograms in mass, less that 1/10 the diameter of a human hair, which enter the body primarily through the airways. According to Wellenius, car and truck traffic is an important source of this pollution, as are oil-fired or coal-fired power plants, manufacturing processes, and the burning of wood.

Many of these particles and other pollutant gases are found in smog. Los Angeles continued its long winning streak as the smoggiest place in the United States again in 2011.

An EPA advisory board has recommended toughening many national standards that would help with particulate pollution, including ozone emissions standards and sulfur content standards for gasoline, but the Obama administration has rejected them, saying they were too costly to industry. A New York Times editorial Monday challenged the White House to approve those sulfur standards and to grant California waivers needed to implement stringent new standards for nitrogen oxides and other pollutants, and to make 1 out of 7 cars emissions-free by 2025.

“The pollutant levels have been going down over the decades, which is good news,” says Jean Ospital, health effects officer for the South Coast Air Quality Management District, the body that enforces air quality standards in the Southland. “The not-so-good news is that our health researchers are finding health effects at ever-lower levels of pollution.”

Ospital points out that health studies usually focus on the long-term effects of air pollution, but this one is extremely short-term, only about 24 hours. Correlations are already known with heart attacks at those concentrations and duration, and now it looks like stroke might be associated with them as well. Under the Clean Air Act, the EPA revises its standards every five years, and a review of the particulate standards is ongoing now.

“Our governing board is very keenly interested in these studies, and it has wholly or partially funded dozens of studies, including the way in which very tiny particles can enter the bloodstream and enter the brain,” says Sam Atwood, a spokesman for the district. “This is just further confirmation that we’re on the right track and we need to accelerate our cleanup efforts. Just because we can see the mountains better than we could 40 years ago, that doesn’t mean that the air is safe.”

The new study was done in Boston, and Wellenius points out that the effects could be vastly different here, depending on weather, behavior of residents and many other factors. But he and his partners in the study did point out that changing the air quality standards could save lives.

“By reducing the number of particles, we could reduce the number of stroke hospitalizations,” he said. “In 2007, by reducing particle levels in the Northeast by 20%, we could have prevented about 6,000 stroke hospitalizations, and that’s just for one year. Carry that forward for multiple years and that’s significant.”

“I think we need to look at this with a nationwide approach to see if this is seen in other cities, to identify which people might be most susceptible, and to identify the sources of pollution that might be most important,” Wellenius added. “In the meantime, the EPA or heath policy people could be considering reviewing the health warnings that accompany release of daily air quality measurements.”

A second study in the same issue of the Archives found that increased air pollution was tied to faster rates of cognitive decline in a test of 20,000 women.

Living next to the freeway -- and don't we all -- is sounding worse all the time.